4 * Copyright IBM, Corp. 2011
7 * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
9 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
10 * See the COPYING.LIB file in the top-level directory.
14 #include "qemu/osdep.h"
16 #include "block/block_int.h"
17 #include "block/blockjob_int.h"
18 #include "qapi/error.h"
19 #include "qapi/qmp/qerror.h"
20 #include "qapi/qmp/qdict.h"
21 #include "qemu/ratelimit.h"
22 #include "sysemu/block-backend.h"
23 #include "block/copy-on-read.h"
27 * Maximum chunk size to feed to copy-on-read. This should be
28 * large enough to process multiple clusters in a single call, so
29 * that populating contiguous regions of the image is efficient.
31 STREAM_CHUNK = 512 * 1024, /* in bytes */
34 typedef struct StreamBlockJob {
37 BlockDriverState *base_overlay; /* COW overlay (stream from this) */
38 BlockDriverState *above_base; /* Node directly above the base */
39 BlockDriverState *cor_filter_bs;
40 BlockDriverState *target_bs;
41 BlockdevOnError on_error;
42 char *backing_file_str;
46 static int coroutine_fn stream_populate(BlockBackend *blk,
47 int64_t offset, uint64_t bytes)
49 assert(bytes < SIZE_MAX);
51 return blk_co_preadv(blk, offset, bytes, NULL, BDRV_REQ_PREFETCH);
54 static int stream_prepare(Job *job)
56 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
57 BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
58 BlockDriverState *base;
59 BlockDriverState *unfiltered_base;
60 Error *local_err = NULL;
63 /* We should drop filter at this point, as filter hold the backing chain */
64 bdrv_cor_filter_drop(s->cor_filter_bs);
65 s->cor_filter_bs = NULL;
67 base = bdrv_filter_or_cow_bs(s->above_base);
68 unfiltered_base = bdrv_skip_filters(base);
70 if (bdrv_cow_child(unfiltered_bs)) {
71 const char *base_id = NULL, *base_fmt = NULL;
72 if (unfiltered_base) {
73 base_id = s->backing_file_str ?: unfiltered_base->filename;
74 if (unfiltered_base->drv) {
75 base_fmt = unfiltered_base->drv->format_name;
78 bdrv_set_backing_hd(unfiltered_bs, base, &local_err);
79 ret = bdrv_change_backing_file(unfiltered_bs, base_id, base_fmt, false);
81 error_report_err(local_err);
89 static void stream_clean(Job *job)
91 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
93 if (s->cor_filter_bs) {
94 bdrv_cor_filter_drop(s->cor_filter_bs);
95 s->cor_filter_bs = NULL;
101 /* Reopen the image back in read-only mode if necessary */
102 if (s->bs_read_only) {
103 /* Give up write permissions before making it read-only */
104 bdrv_reopen_set_read_only(s->target_bs, true, NULL);
107 g_free(s->backing_file_str);
110 static int coroutine_fn stream_run(Job *job, Error **errp)
112 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
113 BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
116 uint64_t delay_ns = 0;
118 int64_t n = 0; /* bytes */
120 if (unfiltered_bs == s->base_overlay) {
121 /* Nothing to stream */
125 len = bdrv_getlength(s->target_bs);
129 job_progress_set_remaining(&s->common.job, len);
131 for ( ; offset < len; offset += n) {
135 /* Note that even when no rate limit is applied we need to yield
136 * with no pending I/O here so that bdrv_drain_all() returns.
138 job_sleep_ns(&s->common.job, delay_ns);
139 if (job_is_cancelled(&s->common.job)) {
145 ret = bdrv_is_allocated(unfiltered_bs, offset, STREAM_CHUNK, &n);
147 /* Allocated in the top, no need to copy. */
148 } else if (ret >= 0) {
149 /* Copy if allocated in the intermediate images. Limit to the
150 * known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE). */
151 ret = bdrv_is_allocated_above(bdrv_cow_bs(unfiltered_bs),
152 s->base_overlay, true,
154 /* Finish early if end of backing file has been reached */
155 if (ret == 0 && n == 0) {
161 trace_stream_one_iteration(s, offset, n, ret);
163 ret = stream_populate(s->blk, offset, n);
166 BlockErrorAction action =
167 block_job_error_action(&s->common, s->on_error, true, -ret);
168 if (action == BLOCK_ERROR_ACTION_STOP) {
175 if (action == BLOCK_ERROR_ACTION_REPORT) {
180 /* Publish progress */
181 job_progress_update(&s->common.job, n);
183 delay_ns = block_job_ratelimit_get_delay(&s->common, n);
189 /* Do not remove the backing file if an error was there but ignored. */
193 static const BlockJobDriver stream_job_driver = {
195 .instance_size = sizeof(StreamBlockJob),
196 .job_type = JOB_TYPE_STREAM,
197 .free = block_job_free,
199 .prepare = stream_prepare,
200 .clean = stream_clean,
201 .user_resume = block_job_user_resume,
205 void stream_start(const char *job_id, BlockDriverState *bs,
206 BlockDriverState *base, const char *backing_file_str,
207 BlockDriverState *bottom,
208 int creation_flags, int64_t speed,
209 BlockdevOnError on_error,
210 const char *filter_node_name,
213 StreamBlockJob *s = NULL;
214 BlockDriverState *iter;
216 int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
217 BlockDriverState *base_overlay;
218 BlockDriverState *cor_filter_bs = NULL;
219 BlockDriverState *above_base;
223 assert(!(base && bottom));
224 assert(!(backing_file_str && bottom));
228 * New simple interface. The code is written in terms of old interface
229 * with @base parameter (still, it doesn't freeze link to base, so in
230 * this mean old code is correct for new interface). So, for now, just
231 * emulate base_overlay and above_base. Still, when old interface
232 * finally removed, we should refactor code to use only "bottom", but
233 * not "*base*" things.
235 assert(!bottom->drv->is_filter);
236 base_overlay = above_base = bottom;
238 base_overlay = bdrv_find_overlay(bs, base);
240 error_setg(errp, "'%s' is not in the backing chain of '%s'",
241 base->node_name, bs->node_name);
246 * Find the node directly above @base. @base_overlay is a COW overlay,
247 * so it must have a bdrv_cow_child(), but it is the immediate overlay
248 * of @base, so between the two there can only be filters.
250 above_base = base_overlay;
251 if (bdrv_cow_bs(above_base) != base) {
252 above_base = bdrv_cow_bs(above_base);
253 while (bdrv_filter_bs(above_base) != base) {
254 above_base = bdrv_filter_bs(above_base);
259 /* Make sure that the image is opened in read-write mode */
260 bs_read_only = bdrv_is_read_only(bs);
263 /* Hold the chain during reopen */
264 if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) {
268 ret = bdrv_reopen_set_read_only(bs, false, errp);
270 /* failure, or cor-filter will hold the chain */
271 bdrv_unfreeze_backing_chain(bs, above_base);
280 qdict_put_str(opts, "driver", "copy-on-read");
281 qdict_put_str(opts, "file", bdrv_get_node_name(bs));
282 /* Pass the base_overlay node name as 'bottom' to COR driver */
283 qdict_put_str(opts, "bottom", base_overlay->node_name);
284 if (filter_node_name) {
285 qdict_put_str(opts, "node-name", filter_node_name);
288 cor_filter_bs = bdrv_insert_node(bs, opts, BDRV_O_RDWR, errp);
289 if (!cor_filter_bs) {
293 if (!filter_node_name) {
294 cor_filter_bs->implicit = true;
297 s = block_job_create(job_id, &stream_job_driver, NULL, cor_filter_bs,
299 speed, creation_flags, NULL, NULL, errp);
304 s->blk = blk_new_with_bs(cor_filter_bs, BLK_PERM_CONSISTENT_READ,
305 basic_flags | BLK_PERM_WRITE, errp);
310 * Disable request queuing in the BlockBackend to avoid deadlocks on drain:
311 * The job reports that it's busy until it reaches a pause point.
313 blk_set_disable_request_queuing(s->blk, true);
314 blk_set_allow_aio_context_change(s->blk, true);
317 * Prevent concurrent jobs trying to modify the graph structure here, we
318 * already have our own plans. Also don't allow resize as the image size is
319 * queried only at the job start and then cached.
321 if (block_job_add_bdrv(&s->common, "active node", bs, 0,
322 basic_flags | BLK_PERM_WRITE, errp)) {
326 /* Block all intermediate nodes between bs and base, because they will
327 * disappear from the chain after this operation. The streaming job reads
328 * every block only once, assuming that it doesn't change, so forbid writes
329 * and resizes. Reassign the base node pointer because the backing BS of the
330 * bottom node might change after the call to bdrv_reopen_set_read_only()
331 * due to parallel block jobs running.
332 * above_base node might change after the call to
333 * bdrv_reopen_set_read_only() due to parallel block jobs running.
335 base = bdrv_filter_or_cow_bs(above_base);
336 for (iter = bdrv_filter_or_cow_bs(bs); iter != base;
337 iter = bdrv_filter_or_cow_bs(iter))
339 ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
346 s->base_overlay = base_overlay;
347 s->above_base = above_base;
348 s->backing_file_str = g_strdup(backing_file_str);
349 s->cor_filter_bs = cor_filter_bs;
351 s->bs_read_only = bs_read_only;
353 s->on_error = on_error;
354 trace_stream_start(bs, base, s);
355 job_start(&s->common.job);
360 job_early_fail(&s->common.job);
363 bdrv_cor_filter_drop(cor_filter_bs);
366 bdrv_reopen_set_read_only(bs, true, NULL);